1. Technical Field
This invention relates generally to roadway barriers, and more specifically to an improved non-redirective gating crash cushion apparatus for all types of roadway barriers including moveable, permanent and portable barriers.
2. Background Art
Non-redirective, gating, crash cushions are highway safety devices whose primary function is to improve the safety for occupants of errant vehicles that impact the end of rigid or semi-rigid barriers or fixed roadside hazards by absorbing the kinetic energy of impact or by allowing controlled penetration or gating of the vehicle. These devices are designed to safely capture or change the direction of an errant vehicle away from roadside or median hazards. These types of systems are typically applied to locations where redirective type impacts are very unlikely to occur.
The crash cushion apparatus of this invention provides an improved non-redirective gating crash cushion apparatus for all types of roadway barriers including moveable, permanent and portable barriers. The inventive apparatus preferably includes a nosepiece assembly, at least one and preferably a plurality of impact absorption elements or modules, and a transition/attachment assembly. The number Of impact absorption elements to be utilized in a particular application is based upon the performance level needed (i.e., the design speed and capacity). The transition/attachment assembly varies with respect to the type of roadway barrier being used, and to which the inventive apparatus is attached.
The impact absorption elements are composed of a plastic container, steel side bars, end plate/hinge assemblies, an evaporation prevention cap with tether, and appropriate fasteners. The first element of the assembled system is preferably left empty of fluid with the evaporation prevention cap installed. All other elements of the system should be filled with fluid in accordance with the installation instructions, and the evaporation prevention caps should be securely installed.
The impact absorption elements each have a forward end and a rearward end, one end (e.g., the forward end) preferably bearing an end-piece with a moveable linkage for attachment to the rear of another element, and the other end (e.g., the rearward end) preferably having no such linkage. Each impact absorption element has two sides, each side bearing at least one vertical indentation, with one side bearing a first number of vertical indentations (e.g., n=1, where n is the number of indentations on a side), and the other side bearing at least one more vertical indentation than the first side (e.g., n=2 or more). In the preferred embodiment, one side bears one vertical indentation, while the other side bears two vertical indentations, each one of those offset from the single vertical indentation on the other side.
When a plurality of impact absorption elements are assembled, the elements should be arranged so that adjacent elements alternate the number of vertical indentations on their respective sides, e.g., if the first element in the assembled system has one vertical indentation on the right side, the adjacent (second) element should have two vertical indentations on its right side, the next (third) element should have one vertical element in its right side, and so forth. The left sides of the assembled system would thus also have alternating numbers of vertical indentations in their sides, e.g., two in the first, one in the second, two in the third, and so forth.
This arrangement of asymmetry in the number of vertical indentations in the opposite sides of an individual impact absorption element, and the alternating of the number of vertical indentations on the same sides of adjacent elements yields desirable and beneficial energy-absorbing deformation characteristics for the individual elements, as well as the assembled system. Specifically, due to this arrangement of asymmetry the elements tend to compress in a non-linear (e.g., zig-zag) fashion upon longitudinal impact, imparting a beneficial energy-absorbing movement to the assembled elements. This causes an effective short column buckle to form, instead of the long column going into long column (Euler) buckling.
The inventive system is also easy to install, and is easier to restore after an impact than other non-redirective crash cushions. For example, sand barrel arrays are significantly wider, and are considerably more difficult to clean and reinstall after a vehicle impact. Non-energy absorbing terminals utilizing an aluminum xe2x80x9cboxxe2x80x9d with internal cells are more costly, and do not provide the equivalent level of energy absorption as the instant invention.